Combination locks have, of course, achieved considerable commercial success, but attempts to manufacture and market relatively inexpensive locks have been quite different largely because very inexpensive locks are fairly simple to pick. While the present lock is exemplified as an aftermarket combination lock for pistol cases, the lock has other low costs applications, and hence, the prior art is equally as broad.
A preliminary patentability search resulted in the following collection of U.S. Patents: Enholm, U.S. Pat. No. 428,387; Battershell, U.S. Pat. No. 1,733,772; Legat, U.S. Pat. No. 1,898,974; Ponder, U.S. Pat. No. 2,740,530; Nemsky, U.S. Pat. No. 3,155,230; Esquibel, et al., U.S. Pat. No. 3,514,981; Feinberg, U.S. Pat. No. 3,597,945; Pedro, U.S. Pat. No. 3,865,166; Jones, Re. U.S. Pat. No. 30,139; Ippolito, et al., U.S. Pat. No. 4,187,703; Gordon, U.S. Pat. No. 4,463,847; Terada, et al., U.S. Pat. No. 5,081,855; Jarboe, U.S. Pat. No. 5,125,661; and Blanchard, U.S. Pat. No. 5,322,200.
The Ippolito, et al., U.S. Pat. No. 4,187,703, shows a locking system applied to an envelope defined by a pair of spaced plates, holding a numismatic coin. The Ippolito device has a slide plate 14 with cross slots 16 transversely positioned away from a central longitudinal slot 18. The transversely movable slides are all identical and can be positioned either in a right-hand or left-hand orientation as seen in FIG. 9. This arrangement, however, produces only two positions for each switch and, therefore, yields few combinations.
The Jarboe, U.S. Pat. No. 5,125,661, discloses a plunger-type locking mechanism, but there is really no logic in the lock combination because if all the plungers are depressed, the plunger 19 can be removed regardless of the position of blocks 35. Thus, it is not really a true combination lock at all.
The Esquibel, et al., U.S. Pat. No. 3,514,981, discloses a plunger-type locking mechanism for a box wherein a locking bar 14 is held or released by a plurality of slide bars 13 that have second slots 30 all positioned the same distance from the inner ends of the bars, and first slots 29 positioned in varying locations to correspond to one of the indicia on area 33 of the projecting ends of the bars 13. When the bars are slid to the appropriate indicia, the slots 29 permit the release of bars 14. The Esquibel, et al. lock has a total of only 48 combinations possible with five bars 13.
It is a primary object of the present invention to ameliorate the problems noted in the prior art above and provide a low cost combination lock that is considerably more tamper-proof than prior art constructions while at the same time having a greater number of possible combinations.
In our parent application, U.S. Ser. No. 08/853,941, a low cost tamper resistant combination lock is provided that combines a high number of possible combinations with improved tamper resistance. That lock included a one piece molded plastic housing having a through bore that receives a one piece plastic plunger having a plurality of integral spherical obstructions. The housing has a plurality of transverse slots each receiving one of two identical blocking slides that snap between three distinct positions, one passing the spherical obstructions and two blocking the obstructions and plunger. Lock picking was minimized by integral flexible fingers in obstruction passing apertures in the slides that engage the spherical obstructions when the slides are in the plunger passing position to simulate the slide blocking positions as the lock picker tugs the plunger.
The housing had a plurality of rivet head shaped bottom projections that can pass through apertures in a flexible pistol case enabling the lock to be used to engage and lock the zipper tang of the case in its zipper closed position.
In the parent application, the first of the two blocking slides is rectangular in configuration and has a central through bore that has a diameter slightly larger than the plunger's spherical obstructions and side slots extending laterally from the central aperture that receive the small diameter portions of the plunger between the spherical obstructions when this slide is in its two blocking positions on either side of the central aperture. Both sides of this blocking slide have side recesses aligned with the ends of the slot that receive the spherical plunger projections when in the blocking positions providing a snap action movement of the blocking slide between its three positions when tension is applied to the plunger.
This snap action not only facilitates the use of the blocking slides but also improves tamper resistance because the lock picker feels the same snap action when moving from the blocking position to the pass position or from the pass position to one of the blocking positions.
To further enhance tamper resistance, a plurality of integral tabs or spring fingers were formed in the central passing aperture in the slides, and they engage the spherical obstructions when the slide is in the passing position. Thus, if the lock picker tugs on the plunger when the slide is in its passing position(but still blocked by other blocking slides), the spherical obstruction will hit the spring fingers causing that particular slide to shift slightly in the slot in a longitudinal direction the same as the slides do when in the blocking position. In this way the lock picker cannot distinguish between the slight shifting movement of the slide in the blocking position and the slides in the passing position when he tugs longitudinally on the plunger.
The second blocking slide was similar to the first except that the passing aperture is in the side position and the slot is a lateral slot extending from the aperture through the central position to the opposite side position. This slide has the same spherical receiving recesses as the first blocking slide formed on both surfaces. This second slide can be reversed in the housing slots to provide both left-hand and right-hand passing thereby increasing the possible combinations without any additional cost.
The slides had flexible fingers adjacent the passing position for the plunger that flex radially outwardly to permit the plunger obstructions to pass there-through. These slides are prevented from falling out of the lock body when the plunger is completely withdrawn by an integral leaf spring formed on the slides that engage one side of the housing slots. The lower side of the slides had three recesses that are selectively received in a projection or detent in the bottom of the slot to selectively hold the slide in one of its three positions.